1. Field of the Invention
This invention related to methods for lessening restenosis of body lumens, and to prosthesis for delivering drugs to treat said restenosis.
2. Description of the Related Art
Restenosis is defined as the reclosure of a previously stenosed ans subsequently dilated peripheral or coronary vessel. It occurs at a rate of 20-50% for these procedures and is dependent on a number of clinical and morphological variables. Restenosis may begin shortly following an angioplasty procedure, but usually ceases at the end of approximately six (6) months. There is not a current therapeutic procedure that has been proven to significantly reduce this restenosis rate.
A recent technology that has been developed that assesses the problem of restenosis is intravascular stents. Stents are typically metallic devices that are permanently implanted (expanded) in coronary and peripheral vessels. The goal of these stents is to provide a long-term "scaffolding" or support for the diseased (stenosed) vessels. The theory being, if you can support the vessel from the inside, the vessel will not close down or restenose. Unfortunately, initial data from clinical stent implants indicates that these metallic structures are not very successful in reducing restenosis.
Pharmacologic (biochemical) attempts have been made to reduce the rate of restenosis. All of these attempts have dealt with the systemic delivery of drugs via oral, intravascular or intramuscular introduction. Little, if any success has been achieved with this systemic approach.
For drug delivery, it has been recognized for a long period of time that pills and injections may not be the best mode of administration. It is very difficult with these types of administration to obtain constant drug delivery. Patient noncompliance with instructions is also a problem. Through repeated does, these drugs often cycle through concentration peaks and valleys, resulting in time periods of toxicity and ineffectiveness. Thus, localized drug treatment is warranted.